1. Field of the Invention
The present invention relates to a two-group zoom lens system and an electronic imaging apparatus equipping the two-group zoom lens system which are used especially for a digital camera and a video camera in which thinning of the apparatus is realized by improving optical-system portions of the zoom lens system.
2. Description of the Related Art
In recent years, a zoom lens system has been generally used as a photographing lens for an electronic imaging apparatuses, such as a digital camera. Further, for achieving miniaturization of the electronic imaging apparatuses, such as a digital camera, etc., demand for thinning the zoom lens as a photographing lens is increasing. Therefore, the miniaturization of the lens which constitutes the zoom lens used for the digital camera has been attempted.
However, if the lens which constitutes the zoom lens is made small manufacture error of the lens parts constituting the zoom lens, and attachment error generated in attaching to a lens holding body will become relatively larger than those in the former constitution.
Even if in the case where the manufacture error of lens part, the attachment error to the lens holding body, etc., can be disregarded, there is a case that by expansion of a lens holding frame and the lens itself due to the influence of change of temperature or humidity etc., an actual light receiving surface position of an image sensor to a zoom lens and a predetermined image forming surface position may not be coincided.
So, in a zoom lens having focusing mechanism, a lens group which is moved when focusing is performed, performs focusing, and simultaneously, corrects shift of the position of an image surface generated between the position of a predetermined image forming surface, and the position of the actual light receiving surface.
However, in such case that the lens group which is moved when focusing is performed simultaneously, carries out correction of the shift of the image surface position between the position of the predetermined image forming surface and the actual light receiving surface position besides carrying out focusing, since it is necessary to secure a domain for movement of a lens group which is moved when focusing is performed, and to keep allowance in the interval between each of lens groups, it is difficult to achieve shortening of a full length of the zoom lens.
Generally, in the zoom lens which consists of two or more lens groups, magnification is performed by changing interval between two or more lens groups when the magnification is performed. However, for achieving miniaturization when a zoom lens is contained in a camera, it is possible to adopt a zoom lens having two groups which are of the minimum numbers of lens group. Technology relating to two-group zoom lens aiming at such magnification and miniaturization has been proposed in Toku Kai No. 2004-102211: Published Unexamined Patent Application.
The zoom lens shown in the publication, has in order from the object side, a lens-group A having negative refracting power, and a lens-group B having positive refracting power, wherein the lens group B having three meniscus lenses with convex surfaces directed toward the object side, and it is constituted so that magnification is performed by moving the lens-group A and the lens-group B, and in order to perform focusing from the infinite distance to the nearest position state, the first lens group is moved toward the object side.